diff --git a/bin/spack b/bin/spack
index a0ce203d63..c63178b191 100755
--- a/bin/spack
+++ b/bin/spack
@@ -44,6 +44,7 @@ try:
     working_dir = os.getcwd()
 except OSError:
     os.chdir(SPACK_PREFIX)
+    working_dir = SPACK_PREFIX
 
 # clean up the scope and start using spack package instead.
 del SPACK_FILE, SPACK_PREFIX, SPACK_LIB_PATH
diff --git a/lib/spack/llnl/util/filesystem.py b/lib/spack/llnl/util/filesystem.py
index 80341f3ddc..11c3dee604 100644
--- a/lib/spack/llnl/util/filesystem.py
+++ b/lib/spack/llnl/util/filesystem.py
@@ -23,19 +23,91 @@
 # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 __all__ = ['install', 'expand_user', 'working_dir', 'touch', 'mkdirp',
-           'join_path', 'ancestor', 'can_access']
+           'join_path', 'ancestor', 'can_access', 'filter_file', 'change_sed_delimiter']
 
 import os
+import sys
 import re
 import shutil
 import errno
 import getpass
 from contextlib import contextmanager, closing
+from tempfile import NamedTemporaryFile
 
 import llnl.util.tty as tty
 from spack.util.compression import ALLOWED_ARCHIVE_TYPES
 
 
+def filter_file(regex, repl, *filenames):
+    """Like sed, but uses python regular expressions.
+
+       Filters every line of file through regex and replaces the file
+       with a filtered version.  Preserves mode of filtered files.
+
+       As with re.sub, ``repl`` can be either a string or a callable.
+       If it is a callable, it is passed the match object and should
+       return a suitable replacement string.  If it is a string, it
+       can contain ``\1``, ``\2``, etc. to represent back-substitution
+       as sed would allow.
+    """
+    # Keep callables intact
+    if not hasattr(repl, '__call__'):
+        # Allow strings to use \1, \2, etc. for replacement, like sed
+        unescaped = repl.replace(r'\\', '\\')
+        repl = lambda m: re.sub(
+            r'\\([0-9])', lambda x: m.group(int(x.group(1))), unescaped)
+
+    for filename in filenames:
+        backup = filename + "~"
+        shutil.copy(filename, backup)
+        try:
+            with closing(open(backup)) as infile:
+                with closing(open(filename, 'w')) as outfile:
+                    for line in infile:
+                        foo = re.sub(regex, repl, line)
+                        outfile.write(foo)
+        except:
+            # clean up the original file on failure.
+            shutil.move(backup, filename)
+            raise
+
+
+def change_sed_delimiter(old_delim, new_delim, *filenames):
+    """Find all sed search/replace commands and change the delimiter.
+       e.g., if the file contains seds that look like 's///', you can
+       call change_sed_delimeter('/', '@', file) to change the
+       delimiter to '@'.
+
+       NOTE that this routine will fail if the delimiter is ' or ".
+       Handling those is left for future work.
+    """
+    assert(len(old_delim) == 1)
+    assert(len(new_delim) == 1)
+
+    # TODO: handle these cases one day?
+    assert(old_delim != '"')
+    assert(old_delim != "'")
+    assert(new_delim != '"')
+    assert(new_delim != "'")
+
+    whole_lines = "^s@([^@]*)@(.*)@[gIp]$"
+    whole_lines = whole_lines.replace('@', old_delim)
+
+    single_quoted = r"'s@((?:\\'|[^@'])*)@((?:\\'|[^'])*)@[gIp]?'"
+    single_quoted = single_quoted.replace('@', old_delim)
+
+    double_quoted = r'"s@((?:\\"|[^@"])*)@((?:\\"|[^"])*)@[gIp]?"'
+    double_quoted = double_quoted.replace('@', old_delim)
+
+    repl = r's@\1@\2@g'
+    repl = repl.replace('@', new_delim)
+
+    for f in filenames:
+        filter_file(whole_lines, repl, f)
+        filter_file(single_quoted, "'%s'" % repl, f)
+        filter_file(double_quoted, '"%s"' % repl, f)
+
+
 def install(src, dest):
     """Manually install a file to a particular location."""
     tty.info("Installing %s to %s" % (src, dest))
diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 904c6262c8..58796d8854 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -33,7 +33,8 @@
 # TODO: it's not clear where all the stuff that needs to be included in packages
 #       should live.  This file is overloaded for spack core vs. for packages.
 __all__ = ['Package', 'when', 'provides', 'depends_on',
-           'patch', 'Version', 'working_dir', 'which', 'Executable']
+           'patch', 'Version', 'working_dir', 'which', 'Executable',
+           'filter_file', 'change_sed_delimiter']
 
 import os
 import tempfile
diff --git a/var/spack/packages/tau/package.py b/var/spack/packages/tau/package.py
new file mode 100644
index 0000000000..373c51c8b8
--- /dev/null
+++ b/var/spack/packages/tau/package.py
@@ -0,0 +1,20 @@
+from spack import *
+
+class Tau(Package):
+    """A portable profiling and tracing toolkit for performance
+       analysis of parallel programs written in Fortran, C, C++, UPC,
+       Java, Python."""
+    homepage = "http://www.cs.uoregon.edu/research/tau"
+    url      = "http://www.cs.uoregon.edu/research/paracomp/tau/tauprofile/dist/tau-2.23.1.tar.gz"
+
+    versions = { '2.23.1' : '6593b47ae1e7a838e632652f0426fe72', }
+
+    def install(self, spec, prefix):
+        # TAU isn't happy with directories that have '@' in the path.  Sigh.
+        change_sed_delimiter('@', ';', 'configure')
+        change_sed_delimiter('@', ';', 'utils/FixMakefile')
+        change_sed_delimiter('@', ';', 'utils/FixMakefile.sed.default')
+
+        # After that, it's relatively standard.
+        configure("-prefix=%s" % prefix)
+        make("install")